1. Field of the Invention
The present invention relates to a jig for positioning a single crystal ingot with respect to the clamp rotary shafts of a device for grinding the peripheral surface of this ingot.
2. Description of the Related Art
A single crystal ingot grown by a CZ or FZ method is formed into a cylinder by the following processes:
(1) Both ends of the single crystal ingot are cut perpendicularly to the axial direction thereof so as to form a cylinder like body.
(2) As shown in FIG. 5, clamp rotary shafts 31L and 31R are pressed against cut surfaces 21L and 21R of the single crystal ingot 20 to clamp it slightly. Gauges 70 and 71 are fixed above both ends of the single crystal ingot 20. Movable pins of the gauges for detecting the shape of the single crystal ingot 20 are brought into elastic contact with the periphery of the ingot 20. Under the above conditions, the single crystal ingot 20 is rotated, and the gauges 70 and 71 measure the peripheral shape of the ingot 20 as displacements of the ends of the movable pins so that the positional deviations between a center of the cut surface 21L and the axis of the clamp rotary shaft 31 and between a center of the cut surface 21R and the axis of the clamp rotary shaft 31R are computed.
(3) The rotation of the single crystal ingot 20 is stopped, and the ends of the single crystal ingot 20 are forced with a hammer into a new position to minimize such positional deviation.
(4) The above processes (2) and (3) are repeated until there is no substantial positional deviation.
(5) The single crystal ingot 20 is tightly clamped by the clamp rotary shafts 31L and 31R, and is rotated. A grinding stone is brought into contact with the peripheral surface of the single crystal ingot 20 while it is moving, thus grinding it into a cylinder.
However, when the single crystal ingot 20 is clamped in process (1), it is positioned by visual observation; consequently, there is a relatively large amount of positional deviation from the ideal. To correct this deviation, the single crystal ingot 20 must be forced into a new position with a hammer several times, thus producing an unfavorable effect on the quality of the ingot 20 by the external mechanical shock.
Furthermore, it is necessary to repeat process (2) to accurately position the single crystal ingot. Thus, such an operation is complicated and time-consuming.